Answer: (x-3)(x-3)
This is a perfect square trinomial in the form a^2 - 2ab + b^2 = (a-b)^2. In this case, a = x and b = -3.
Another way you can look at it is to ask yourself "what two numbers multiply to 9 (last term) and add to -6 (middle coefficient)?". Those two numbers are -3 and -3
-3 plus -3 = -6
-3 times -3 = 9
So this is why x^2-6x+9 = (x-3)(x-3)
We can expand (x-3)(x-3) back out to get x^2-6x+9 again using the FOIL rule, distributive property, or the box method.
